Mounting hole for proximity switch - mod to spider?

When mounting the Z proxy sensor, I had the following requirements:

• No interference with dust collector piping
• LED on sensor was visable
• Safe location that wasn't likely to be hit
• No modifications or holes in the Z-slide
• No major fabrication
• Looked "professional"

I think I met the desgin goals. It does require that you have the 6-roller setup. It only requires a washer with an ID of the OD of your proxy (mine are 18mm). I used a smaller washer and then drilled out the center to make it a little more compact. This mounting location also keeps the wiring inside the Y-car, instead of on top of it.

It could be improved by making a "slot" so that the proxy can be moved up and down to adjust when it comes on (mine comes on about 1/2" before it hits the hard stop. I'm guessing that the slide could even be adjusted to leave a slot in the 45 degree angle (if there is enough width.) Here is a video of the sensor in action:

http://www.youtube.com/v/ScJRB9qr_lg

Here are some photos before and after mounting:

[Gerald D]

Anybody see any problems if the lasered spider plate is modified to take a proximity switch like this:

0001.jpg

[Doug_Ford]

I just went out and looked at my machine and I can't see any problem with it. In fact, this type of mounting would allow a 6 inch dust collection system to fit perfectly.

[astrolavista]

Here's what this configuration looks like with a 4" pipe

[Gerald D]

Rene, what are you using as "targets" for the proximity sensor?

[Gerald D]

Does the switch perhaps not get too close to the gas spring? Would it be better if the switch was on the z-motor side? (Deeper down in the y-car to miss the motor mount)

[astrolavista]

HI Gerald,

I drilled a .5" hole in the "corner" of the 1x2, I was thinking of mounting it lower.. but a. I like to see the led that it is active.. b. I though if drilling the targets had any detrimental affects to the z slide assembly, the futher from the ends I could get them (the target holes) the better.. Make sense? After it was built I was thinking I could have made my bracket alittle taller to pervent the wire chaffing on the y car.

R

[Gerald D]

I would use target holes for the Z (like we use holes for X & Y) because we don't have the chance of the Z jumping off the rails. I would use lumps instead of holes. (Holes could weaken the slide)

[Doug_Ford]

Hmmmm....maybe it wouldn't handle with a 6 inch duct. However, I bet if I bent the mounting a little bit, it would still work. Thanks Rene.

[Gerald D]

A 6" duct would lie more to the back of the y-car, if you really wanted such a huge sucker. It will stlll miss the switch.

For those using z proximity switches, have you EVER found the right position for a target for the lowest Z slide limit? I believe that is an impossibility. A single target point to "home" the Z-slide at the top of its travel should be all that is required. In this case a "hole" target could be used if the proxy is mounted very low on the spider - the hole would not be in a high stress area. Any thoughts?

[Alan_c]

All the "Big Iron" machines I have worked on (MultiCam, Biesse & SCM) have only one limit/home ref at the uppermost position of the Z- slide. As you say it is impossible to fix a lower position as the safe position will vary according to bit length, material depth etc etc. One at the top will be sufficient.

[javeria]

One one of the chinese machines my friend has - found out that the proximity is just 1.5 inch long , that might solve so much!

[Gerald D]

Short switches are very common - I am actually surprised to see that the typical MechMate'r buys the long switches.

[domino11]

Is there any difference in performace of long switches or short ones? I realize that there is a difference in sensing distance from shrouded to unshrouded.

[Gerald D]

There is no difference in performance. The long ones are offered to reach deeper into machinery, and are maybe regarded as more universally useful.

[MattyZee]

I remember seeing this post a while ago and thought it looked like a neat solution to this problem. Haven't got my Z axis together yet so i'm sot sure how to actually implement the target for this location. But i like the fact its a little more out-of-the-way.

Probably not that easy to incorporate into the spider laser cut part without complicating the bending. (you could have the washer built into the spider and not bend that part when you bend the spider, but that may be making things too hard)

[melissa]

I'm trying to decide where to mount the Z proxy.

After looking at the photos in post #3 above: http://www.mechmate.com/forums/showt...38&postcount=3 , I got to wondering about using the body of the gas shock as the proxy target.

With a little bracket to hold the proxy in the right position, the wide part of the shock is normally in the sensor's view. When the slide moves to its upper limit, the wide part moves out of view, triggering the sensor.

Thoughts?

[smreish]

A better "hunk of metal" to detect is the rack and pinion on the alternate side of the slide. Just mirror the pictures you linked to. I personally used 3 different locations on alternate machines. All worked well.
- bottom of slide on one machine
- middle back of one, by using the drawbolt as the "sense"
- rack and pinion on another.

It all comes down to what works physically for you.

Good luck.

[smreish]

Red,

I had to sit and really think about your dialog with Steve. I searched the forum for the time when the R&D of this decision was made for our prox circuit. The dialog from Feb 2008 is such between myself, Gerald and Mike R. To be clear, the decision on this circuit was based on this conversation and few noted key points:

Notes:

- Machine must detect the rail always and fault when it doesn't (no metal present) This is a derail situation
- Machine must detect the hole in the end of travel (EOT) position
- Sensor must isolate the the machine for EMF interference to the PMDX
- Sensor must keep machine from running if not working (power supply fault, sensor fault, etc.)
- Sensor must be wired in series so a single contact closure will result in the "homing routine" found within MACH 3 without modification
- Relay bank is easily expandable to accommodate additional axis' of use on the machine. Thus, homing a 4th (b) or 5th (c) axis without significant wiring changes outbound on the machine, thus keeping the mod's in the control cabinet.

That conversation is here:

"Mike,

the metal targets will be present in front of the proxys in the "normal" condition. In the presence of that metal, the NO switches will close."

The targets are "abnormal" in this case - we are not trying to sense bolt heads or lumps of metal at the ends of travel. We look at the rail all the time, but there are holes at the end of the rails. When the proxy sees the hole, it changes state and opens the relay. Also when the car jumps off the rail.

Gerald,

Sorry. I should have remembered that the sensors are actually going 'active' when they sense the 'hole', which, as you pointed out, makes Sean's circuit work perfectly.


I trust Steve's advice for his circuit knowledge and board manufacturing, but do to the nature of "why and how" the detection circuit is utlized in the MM is non-standard.

Either using the sink/source option with the PMDX card as the solo interface to the sensors or a relay is truly choice. Each has a consequence, but works. I hope this helps you in your decision process.

Best,
Sean

[Gerald D]

Also realise that the z-axis is a different animal to the x- and y- axes. The z cannot lift off a rail and the really important end of the z-axis (the bottom) is impossible to "home" because the top surface of the workpiece (or spoilboard) is a variable position.